1. Field of the Invention
The application relates to a method utilized in a wireless communication system and a communication device thereof, and more particularly, to a method of handling measurement gap configuration in a wireless communication system and a related communication device.
2. Description of the Prior Art
A long-term evolution (LTE) system, initiated by the third generation partnership project (3GPP), is now being regarded as a new radio interface and radio network architecture that provides a high data rate, low latency, packet optimization, and improved system capacity and coverage. In the LTE system, an evolved universal terrestrial radio access network (E-UTRAN) includes a plurality of evolved Node-Bs (eNBs) and communicates with a plurality of mobile stations, also referred as user equipments (UEs).
In the LTE system, an UE may perform measurement to measure communication quality, such as quality of a frequency channel or strength of a radio signal, which is controlled by the E-UTRAN, due to mobility of the UE. Measurement can be divided into two types according to the current operating frequency of the UE, which are an intra-frequency measurement and an inter-frequency/inter-RAT measurement. The intra-frequency measurement is predominantly performed for the mobility within the same frequency channel (i.e. between cells with the same carrier frequency), whereas the inter-frequency/inter-RAT measurement is predominantly performed for the mobility between different frequency channels (i.e. between cells with a different carrier frequency). In addition, the inter-frequency/inter-RAT measurement is performed during uplink/downlink idle periods, such as a measurement gap configured by the network. During the measurement gap, both the uplink and downlink transmissions are prohibited (e.g. no PUCCH, PUSCH, PDCCH, and PDSCH transmissions), and thereby the inter-frequency/inter-RAT measurement can be performed within the measurement gap.
Toward advanced high-speed wireless communication system, such as transmitting data in a higher peak data rate, LTE-Advanced system is standardized by the 3rd Generation Partnership Project (3GPP) as an enhancement of LTE system. LTE-Advanced system targets faster switching between power states, improves performance at the cell edge, and includes subjects, such as bandwidth extension, coordinated multipoint transmission/reception (COMP), uplink multiple input multiple output (MIMO), etc.
For bandwidth extension, carrier aggregation is introduced to the LTE-Advanced system for extension to wider bandwidth, where two or more component carriers are aggregated, for supporting wider transmission bandwidths (for example up to 100 MHz) and for spectrum aggregation. According to carrier aggregation capability, multiple component carriers are aggregated into overall wider bandwidth, where the UE can establish multiple links corresponding to the multiple component carriers for simultaneously receiving and/or transmitting.
In the LTE system, measurement functionality is defined for the UE supporting a single component carrier. Therefore, the network configures a measurement gap to the UE only for the component carrier for measurement. However, in the LTE-Advanced system, the measurement functionality is not clear defined for the UE supporting multiple component carriers. In other words, the network does not know how to configure the measurement gap for the multiple component carriers to the UE for measurement. Improper configuration of the measurement gap may cause packet scheduling problems and transmission interruption. Since data transmission/reception (e.g. the uplink and downlink transmissions) cannot be performed during the measurement gap, transmission/reception performance of the UE is downgraded.